This invention pertains generally to welding systems, and more particularly to an apparatus and method for feeding weld wire to a welding tip of a welding torch in a welding system
Welding wire feed apparatuses, commonly known as wirefeeders, are widely used in a automated and semi-automated welding operations to feed filler wire to a molten pool on a workpiece being heated by a welding torch on a welding system to form a weld.
A conventional, prior art wirefeeder will now be described with reference to FIG. 1. FIG. 1 is a diagrammatic illustration showing a cross-sectional side view of a welding system 10 having a conventional wirefeeder 12. Referring to FIG. 1, a conventional wirefeeder 12 includes a filler wire supply 14, such as a spool, on which filler wire 16 is stored, a wirefeed mechanism 18 mounted to the welding system 10, a wire liner or conduit 20 through which the filler wire is passed from the wirefeed mechanism to an adjustment mechanism 22 attached to a welding torch 24 on the welding system. The adjustment mechanism 22 positions a wire guide 26 through which the filler wire 16 is passed to location or point near to the welding torch 24. Typically, the wirefeed mechanism 18 includes an electric motor 28 driving one or more gears or drive wheels (not shown) that engage the filler wire 16 forcing it through the conduit 20 to the adjustment mechanism 22. The wirefeed mechanism 18 can be operated manually by an operator, or automatically by a controller (not shown) to synchronize feeding of the filler wire 16 to movement of a workpiece (not shown) being welded on the welding system 10.
A disadvantage of conventional wirefeeders 12 is that complicated and cumbersome adjustment mechanisms 22 make it difficult to precisely position the wire guide 26 in relation to the welding torch 24 or workpiece. One commonly used adjustment mechanism 22 involves the use of a number of interconnected dovetail slides or sliding members repositioned by thumbscrews 28. A first dovetail slide allows the wire guide 26 to be moved up and down vertically in relation to the welding torch 24. A second dovetail slide depending from the first allows the wire guide 26 to be moved horizontally, and a third dovetail slide depending from the second allows the wire guide to be moved in and out relative to the welding torch 24. Because the slides are interconnected, adjustment of any one of them can necessitate repositioning of the others, which in turn can lead to the need to reposition the first slide and so on. The adjustment procedure is often made even more difficult by the use of fasteners on the slides which require a wrench, screwdriver or other tool to tighten.
A related problem with the adjustment mechanism 22 of conventional wirefeeders 12 is that it is often difficult or impossible to efficiently or subtly adjust the angle at which the filler wire enters the molten pool on the workpiece, commonly known as the wire entry angle. The entry angle is important because if the filler wire is fed into the molten pool too low, i.e., at too shallow an angle relative to the surface of the workpiece, it can hit the workpiece before entering the molten pool, causing the workpiece to wobble, or the filler wire to stick to the surface of the workpiece. On the other hand, if the wire comes in too high, i.e., at too large an angle relative to the surface of the workpiece, the heat from the welding torch can cause the end of filler wire xe2x80x9cball upxe2x80x9d or burn back without contacting the molten pool. For example, the entry angle for an automated Gas Tungsten Arc Welding (GTAW) welding operations is from about 14 to about 40 degrees relative to the horizontal plane. However, possible entry angles are often constrained by a number of circumstances including workpiece configuration, welding system or process setup, and interference with tooling used to position the workpeice. This is particularly a problem with conventional wirefeeders 12, which are generally designed to provide a single, fixed entry angle determined by the mounting or attachment of the wire guide 26 to the adjustment mechanism 22 that can be changed little if at all, and then only with great difficulty.
Yet another problem with conventional wirefeeders 12 is that the weight of the adjustment mechanism 22 and the wireguide 26, which is not in-line with a centerline of a main body or support structure of the welding system 10, often results in wobbling during the welding operations leading to filler wire deposition irregularities. These irregularities are magnified in a multi-pass buildup processes in which as the filler wire is welded to that deposited on a previous pass to form a flange or knife edge of deposited metal. This situation is exacerbated by adjustment mechanisms, such as the dovetail slides (not shown), in which the brackets and interconnections of components of the adjustment mechanism project a significant distance from the centerline of the main body of the welding system 10. Moreover, conventional prior art wirefeeders typically encompass a single contiguous adjustment mechanism 22 for both fine and course adjustments making fine adjustments difficult. The above is true of all welding operations, including only those in which the welding torch is moved over the workpiece and those in which the workpiece moved under the welding torch.
In addition to the difficulties with the adjustment mechanism and procedure, another significant problem with conventional wirefeeders is the complex and circuitous path the filler wire must take within the conduit from the wirefeed mechanism to the adjustment mechanism. This complex and circuitous path causes binding or constriction of filler wire within the conduit resulting in non-uniform feeding of the filler wire and leading to deposition inconsistencies in the weld. This is particularly a problem for wirefeeders in which the wirefeed mechanism uses gears to engage and drive the filler wire. The gears score the surface of the filler wire producing sharp or rough edges that catch on the inner surface of the conduit, resulting in sharp or rough edges on the inner surface of the conduit that further impede movement of the filler wire through the conduit. One approach to dealing with this shortcoming in conventional wirefeeders involves the regular replacement of the conduit. However, this is not a wholly satisfactory solution since, in addition to the expense and lost operating time of the welding system, it is generally sometime before need to replace the conduit is recognized, and in the meantime binding of the filler wire will lead to welds with deposition inconsistencies necessitating costly reworking or replacement of numerous workpieces.
A related problem involves the juncture between the conduit and the wire guide. The filler wire supply is generally not in-line with the wire guide and because the wire guide is moved during the adjustment procedure prior to the welding operation, if not during the welding operation itself, the conduit can form a sharp bend at this point leading to binding or constriction of filler wire within the conduit.
Accordingly, there is a need for a wirefeeder and method for feeding filler wire to a welding tip of a welding torch in a welding system that reduces or eliminates binding or constriction of the filler wire whereby deposition inconsistencies are reduced or eliminated. There is a need for a wirefeeder and method that reduce or eliminate wobbling by the wirefeeder whereby irregularities in welding are reduced or eliminated. There is yet a further need for a wirefeeder and method that provides a straightforward adjustment mechanism for easy positioning of the wire guide, including easy adjustment of wirefeed entry angles over a wide range of angles.
The present invention provides an apparatus and method for feeding welding or filler wire to a welding tip of a welding torch in a welding system.
In one aspect, the invention is directed to a wire guide assembly or wire guide apparatus having a supply spool on which the filler wire is stored, a drive assembly or drive mechanism attached by a mounting arm to the welding torch of the welding system, a wire liner or conduit through which the filler wire is passed extending from a location near to the supply spool to the drive mechanism, and a guide assembly attached to the drive mechanism to convey the filler wire from the drive mechanism to a point near the welding tip of the welding torch. Generally, the guide assembly is configured so that the filler wire is passed in a substantially straight line from the drive mechanism to a point proximal to the welding tip of the welding torch. The guide assembly includes a bracket by which the guide assembly is attached to the drive mechanism, a wire guide through which the filler wire is passed, and first and second adjustors attached to the bracket of the guide assembly to position the wire guide relative to the welding tip. The first adjustor and the second adjustor are adapted to move the wire guide along axes perpendicular to one another and to a longitudinal axis of the wire guide.
In one embodiment, the first and the second adjustors include gimbals supporting the wire guide. Each of the gimbals is attached to a threaded screw passing through an opening in an arm projecting from the bracket of the guide assembly. Adjusting knobs threadably engaging a portion of each of the screws extending through the openings enable the length of the screws between the gimbal and the opening to be adjusted.
In another embodiment, the mounting arm attaching the drive mechanism to the welding torch includes a bracket attached to the welding torch and a tube member attached the drive mechanism. The tube member is in sliding engagement with the bracket to vary the position of the drive mechanism and the guide assembly relative to the welding torch. The tube member is curved or arced to change the angle formed by an axis of the filler wire and the welding torch, commonly known as the wire entry angle. Preferably, the tube member is curved or arced to provide entry angles ranging from about 10 to about 40 degrees, and more preferably, the tube member is curved or arced to provide entry angles ranging from about 14 to about 32 degrees. Most preferably, components of the wire guide apparatus, i.e., the drive mechanism, guide assembly, and mounting arm are adapted to provide a xe2x80x9chomexe2x80x9d position having an entry angle of from about 14 to about 17 degrees depending on a size or thickness of the filler wire. For example, for filler wire having diameters of 0.035xe2x80x3 or more, 17 degrees is considered by many to be optimum wirefeed entry angles for precise, automated Gas Tungsten Arc Welding (GTAW) applications. For smaller filler wire sizes such as 0.020xe2x80x3 wire, 14 degrees is preferred.
In yet another embodiment, the conduit is a rigid conduit and the supply spool is positioned in relation to the drive mechanism so that it follows a substantially straight path between the supply spool and the drive mechanism. Alternatively, the conduit is a flexible conduit, and the feed apparatus further including a pulley attached to the drive mechanism to allow the drive mechanism to be positioned independent of the supply spool, including positioned on an opposite side of the welding torch from the supply spool.
The wire guide apparatus of the present invention is particularly useful in arc welding systems, such as GTAW systems and Plasma Arc Welding (PAW) systems, and may be useful in electron beam welding (EBW) and laser beam welding (LBW) systems.
In another aspect, the invention is directed to a method of feeding filler wire in a welding system having a welding torch with a welding tip for welding a workpiece using the wire guide apparatus of the present invention. In the method, the filler wire is drawn or pulled from a supply using a drive mechanism attached by a mounting arm to the welding torch. The filler wire is then conveyed from the drive mechanism to the welding tip of the welding torch using a wire guide attached by a bracket to the drive mechanism, the wire guide having a distal end located proximal to the welding tip. The position of the wire guide relative to the welding tip is positioned using first and second adjustors attached to the bracket of the wire guide apparatus.
In one embodiment, the wire guide apparatus has a substantially straight passage through which the filler wire is passed from the drive mechanism, and the step of conveying the filler wire from the drive mechanism to the welding tip of the welding torch involves conveying the filler wire in a substantially straight line from the drive mechanism to the welding tip of the welding torch.
In another embodiment, the first and the second adjustors include gimbals supporting the wire guide, arms attached to the bracket of the guide assembly, and threaded screws attached to the gimbals and extending from the gimbals and through openings in the arms. Length of the screws between the gimbals and the openings are adjusted by turning adjusting knobs threadably engaging a portion of the screws extending through the openings, thereby adjusting the position of the wire guide relative to the welding tip.
Optionally, the wire guide apparatus further includes a controller for controlling operation of the drive mechanism, and the method includes the further step of automatically advancing the filler wire in relation with movement of the welding tip over a workpiece. Preferably, the controller is adapted to advance the filler wire at a first predetermined rate and retract the filler wire at a second, lesser predetermined rate, and the step of automatically advancing the filler wire includes the steps of advancing the filler wire at the first predetermined rate and retracting it at the second predetermined rate.
In yet another aspect, the invention is directed to a welding system for welding a workpiece. The welding system includes a welding torch having a welding tip for heating and forming a weld on the workpiece, and a wire guide apparatus according to the present invention. The wire guide apparatus includes drive means for moving weld wire from a weld wire supply to a location proximal to a welding tip of a welding torch, guide means for positioning the wire guide relative to the welding tip, the guide means attached to the drive means, and adjustment means for adjusting the position of the wire guide relative to the welding tip. Generally, the drive means is attached to the welding torch at a point or location near the welding tip.
In one embodiment, the guide means includes a wire guide through which the filler wire is passed, the wire guide attached by a bracket to the drive means and having a distal end located proximal to a welding tip of the welding torch. Preferably, in one version of this embodiment the adjustment means includes a first adjustor and a second adjustor attached to the bracket to position the wire guide relative to the welding tip, the first and second adjustors are adapted to move the wire guide along axes perpendicular to one another and to a longitudinal axis of the wire guide. More preferably, at least one of the adjustors include a gimbal supporting the wire guide, an arm attached to the bracket of the guide means, a threaded screw attached to the gimbal and extending from the gimbal and passing through an opening in the arm, and an adjusting knob adapted to adjust length of the screw between the gimbal and the opening in the arm.
The advantages of a wire guide apparatus of the present invention include: (i) a wire guide that provides a straight path for filler wire from a drive mechanism to a molten pool on a workpiece; (ii) elimination of wobbling by the wire guide apparatus whereby irregularities in welding are reduced or eliminated; (iii) straightforward positioning adjustment mechanism for easy positioning of the wire guide; (iv) variable and easily adjustable wirefeed entry angles; and (v) elimination of binding or constriction of weld wire whereby deposition inconsistencies are reduced or eliminated.